1. Field of the Invention
This invention relates to devices that can be placed in a conventional chair to aid an occupant in rising from a seated position and also as an aid in lowering to a seated position from standing. The device is of particular value for the weak and the infirm.
2. Brief Description of the Related Art
Many such devices exist and among them is the Uplift Seat Assist, which is a non-powered device which provides a supplementary raising force to a user""s own muscles to aid in rising and sitting. Such device is described in U.S. Pat. No. 5,316,370. The present device is an enhancement of that one, wherein the forces are supplied entirely by an electric motor and mechanism and requires no muscular participation from the user.
The design challenge for a compact personal seat assist device is to design a cushion with a motorized mechanism in as flat a form as possible. The reason for the flatter form is to minimize impact on the comfortable seating height of the standard chair, on which the device is placed. Therefore, the intent of this description is to show a solution to the challenges of producing a stable, safe, easy, and powerful lifting seat cushion, which, in the lowered position, is as thin as possible.
The present invention is directed to an electric lifting cushion or seat assist device which, in a preferred embodiment, includes a seat pivotally secured adjacent one end to a frame or base and which is also connected by a linkage which extends upwardly adjacent opposite sides of the base to one or more bearings associated with an underside of the seat. In a preferred embodiment, the linkage is a generally U-shaped element pivoted in bearings to the base and in pair of bearings to the underside of the seat.
At least one set of generally opposing cam members or plates are secured and extend in off-set manner toward one another from each of the underside of the seat and upwardly from the base which cam members taper downwardly toward the rear portion of the seat assist device. In preferred embodiments, at least two pair of such cam members or plates are provided in spaced relationship with respect to one another extending from each of the seat and the base.
In order to elevate or lower the seat relative to the base, an elevation control member is provided. The control member in a preferred embodiment includes at least one pair of rollers which are engageable one with the cam member extending from the seat and the other with the cam member extending upwardly from the base. In embodiments which incorporate a plurality of cam members or plates, a separate roller set is provided for each opposing pair of cam members.
In accordance with the invention, each pair of rollers are connected to a drive mechanism which is operable upon the activation of an electric motor to move the set of rollers linearly. As the rollers track along the opposing cam surfaces in a first direction toward the front of the seat assist device, the seat will be elevated relative to the base. In a like manner, by reversing the direction of movement, the seat can be lowered relative to the base. In a first embodiment, the operating mechanism is attached to the motor by a pivot coupling such that an angle of inclination of the drive mechanism may be continuously changed depending upon the linear position of the set of rollers.
In preferred embodiments, the rollers are carried by a cross beam member, which also mounts a nut which is traversed by a lead screw which forms part of the drive mechanism. The nut is pivotally carried by the cross beam member such that the beam is pivotal about an axis which is substantially normal to rotational axes of both the rollers and the lead screw so as to compensate for torsional flexure of the seat. In a first preferred embodiment, one end of the lead screw is pivotally connected to a coupling member secured to an output of an electric motor which may be either powered by an AC power source or a DC battery power source. In accordance with the invention, the vertical angle of the lead screw changes depending upon the vertical movement of the roller set relative to the surface of the cam members or plates, such that there is no binding of the lead screw during the linear adjustment of the roller sets to raise and lower the seat relative to the base of the seat assist device.
In other preferred embodiments of the invention, as opposed to having the lead screw pivoted through a coupling connected to the drive motor, the drive motor made be operably connected to the lead screw with the motor and operable connection being mounted to a pivot plate which allows for the angle of inclination of the lead screw to change as the rollers travel along the cam members or plates.
The present invention also incorporates a control mechanism for terminating the activation of the electric motor depending upon the position of the roller sets relative to the opposing cam members or plates. In a preferred embodiment, sets of electrical contacts are mounted in a housing adjacent to the motor. The electrical contacts are bridged by a contact switch which is toggled between the various contacts by being engaged or connected to a slide switch plate at one end and having an opposite end secured to be moved under the influence of an operating handle. The operating handle is connected by a crank shaft to a forward end of the slide switch plate and the slide switch plate is also connected to a resilient member which normally tends to move the slide switch plate such that the electrical contacts of the contact or toggle switch are biased to an open position to prevent the supply of power to the drive motor. By movement of the operating handle in a first direction, the slide switch plate is moved against the spring such that the toggle switch contacts bridge contacts to operate the motor. When pressure is released from the operating handle, the spring returns the slide switch to a position in which electrical contact is disengaged to the motor. If pressure is maintained on the operating handle, the cross beam associated with the roller sets will engage a flange on the slide switch plate to thereby urge the toggle switch to an off position relative to the motor contacts. To reverse the direction of the motor, the handle is moved in a different direction causing the slide switch plate to move the toggle switch contacts to bridge separate motor contacts causing a reverse rotation of the motor which contact is broken when the cross beam associated with the roller sets reaches a position in which an element extending therefrom engages the slide switch plate thereby moving a slide switch plate to move the electrical contacts of the toggle switch to an off position.
It is the primary object of the present invention to provide an electric lifting cushion or electric seat assist device which is very compact in configuration but which provides a lifting force to assist an individual in both rising from a seated position or moving from a standing position to a seated position without the user having to use their own muscles to aid in rising and sitting.
It is another object of a preferred embodiment of the present invention to provide a seat assist device having a seat which is raised and lowered by a low-power electric motor and wherein the mechanical mechanism utilized incorporates one or more roller sets engageable with cam surfaces associated with a seat and base of the device and wherein the one or more roller sets are carried by a memeber which is pivotal about an axis which is substantially normal to the rotational axes of both the rollers and the drive element and which drive element is also either pivotally coupled to the motor such that the drive element may be pivoted in a vertical plane or the motor is operatively connected to the drive element such that the motor and drive element pivot vertically.
It is also an object of the present invention to provide an electric lifting cushion or seat assist device which can be manually controlled by a lever or other operating member which is connected to control the operation of an electric motor mounted to the base of the device such that when the seat associated with the device approaches a fully raised or fully lowered position, power to the motor is automatically terminated.